The point is that Comcast perfectly fits the old notion of monopolists as robber barons, so-called by analogy with medieval warlords who perched in their castles overlooking the Rhine, extracting tolls from all who passed. The Time Warner deal would in effect let Comcast strengthen its fortifications, which has to be a bad idea.
Interestingly, one cliché seems to be missing from the boilerplate arguments being deployed on behalf of this deal: I haven’t seen anyone arguing that the deal would promote innovation. Maybe that’s because anyone trying to make that argument would be met with snorts of derision. In fact, a number of experts — like Susan Crawford of Benjamin N. Cardozo School of Law, whose recent book “Captive Audience” bears directly on this case — have argued that the power of giant telecommunication companies has stifled innovation, putting the United States increasingly behind other advanced countries.
And there are good reasons to believe that this isn’t a story about just telecommunications, that monopoly power has become a significant drag on the U.S. economy as a whole.